In a conventionally known disposition of a counterbalance valve, as it is disclosed, for example, in Japanese Utility Model Application Laid-open No. Sho 54-44390, a counterbalance valve and a relief valve are disposed away from each other in a casing, and both the valves are communicated with each other by means of a plurality of passages.
However, in such a conventional disposition, a relief valve, the construction of which is complicated, is disposed in addition to a counterbalance valve, and further, a plurality of passages communicate the valves with each other. As a result, there are problems that the construction of the whole disposition is very complicated, and that accordingly, its manufacturing cost is expensive.
It is an object of the present invention to provide a counterbalance valve provided with a relief function which is simple in the whole construction.
It is another object of the present invention to provide a counterbalance valve which can be manufactured at a low cost, though it has a relief function.